The present invention generally relates to a universal joint adapted to interconnect two rotating shafts positioned at an angle relative to one another. Specifically, the present invention is a universal joint adapted to allow rotational movement to be transferred between two shaft which are at an angle relative to one another for low torque and low speed applications such as a steering column.
Many universal joints exist which are adapted to transfer rotational movement from an input shaft to an output shaft. The purpose of a universal joint is to allow this rotational movement to be transferred when the input shaft is positioned at some angle relative to the output shaft. Traditional universal joints use a pair of yokes attached to each other with a cross member. Needle bearings located within ball caps supported by the yokes provide flexibility in transmitting rotational motion between the yokes when the yokes are at an angle to each other. This type of universal joint is ideal for high torque and high RPM applications. Examples of such devices include propeller shafts used in front engine, rear wheel drive motor vehicles. However, in some applications, such as with a steering column of a motor vehicle, it is not necessary for the universal joint to be robust enough to withstand high torque and high RPMs. In steering column applications it is desired to connect the steering wheel to the steering gear box. Due to packaging and crash protection issues, those components are generally not aligned.
Universal joints for low torque, low RPM applications have also been developed. One such method involves the use of a head and pocket arrangement wherein the head has a plurality of facets facing radially outward and the pocket has a corresponding plurality of facets facing radially inward. In this type of application, the head is mounted to one of the shafts and is rounded to allow that shaft to tilt relative to the pocket. The meshing engagement of the outwardly facing sides of the head and the inwardly facing sides of the pocket allow rotation movement to be transferred from one shaft to the other similarly to a pair of meshing gears. One problem with such an arrangement is that due to the friction between the head and the pocket, the sides of each will wear with time. As these surfaces wear, there will be less frictional engagement. Ultimately, the head and pocket will wear to a point where there is an unacceptable play or dead-land between the input shaft and the output shaft. Therefore, there is a need for an improved universal joint which will accommodate wear to the head and pocket to maintain solid engagement between the head and the pocket as the head and pocket wear with time.